CAV424 Datasheet, PDF (6/7 Pages) List of Unclassifed Manufacturers – Converter IC for Capacitive Signals

Converter IC for Capacitive Signals
CAV424
It thus follows that the output signal of the low-pass stage is
V_LPOUT = V_DIFF + V_M
with
( ) V_DIFF
= G_LP
⋅V_{DIFF ,0}
= G_LP
⋅³â‹…
8
V_{CX 1} − V_{CX 2}
In order to reduce the number of external components needed for the sensor system a temperature
acquisition sensor was integrated. With the aid of a processor, this sensor can be used to compensate for
the temperature error of the entire sensor system, for example.
FUNCTIONAL DIAGRAM
R_CX1
R_CX2
R_OSC
7
CAV424
T Sensor
12
C_OSC
Reference
Oscillator
16
C_X1
14
C_X2
Integrator 1
Integrator 2
10
Figure 4: functional diagram CAV424
2
3
1
Current Reference
Signal Conditioning
VCC
11
6
C_VM
5
V_DIFF
15
C_L1
13
C_L2
4
R_L1
R_L2
GND
Adjustment:
The zero-adjustment is made by the resistors R_CX1 or R_CX2 for the case that the varying capacitance C_X2
has nearly the same (and its smallest) value as the fixed capacitance C_X1 (reference capacitance). There-
fore one of this resistors is varied until the differential voltage
V_DIFF = V_LPOUT −V_M
is zero:
V_DIFF = 0
analog microelectronics
January 2002
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